The hormone and growth factor requirements of mammalian cells have been observed by several laboratories to change after viral transformation. This project sought to determine whether transformation induced by tumor promoters, such as 12-0-tetradecanoyl-phorbol-13-acetate (TPA), would also effect the hormone and/or growth factor requirements of cells. Toward this goal a hormone and growth factor supplemented defined medium was developed for an epithelial cell line (JB-6 CLONE 41), which undergoes transformation after exposure to TPA. In place of serum, the defined medium contains fibronectin, insulin, transferrin and epidermal growth factor (EGF). In this defined medium the cells can be grown indefinitely, but if EGF is omitted the cells exhibit little or no proliferaiton. Using this defined medium as a starting point, it was determined that a transformed cell line isolated from JB-6 Clone 41 will proliferate in defined media lacking EGF. Thus, these studies indicate that transformation by tumor promoters can lead to altered growth factor requirements.